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A quadrat is a frame used in ecology, geography, and biology to isolate a standard unit of area for study of the distribution of an item over a large area. Quadrats typically occupy an area of 0.25 m2 and are traditionally square, but modern quadrats can be rectangular, circular, or irregular. A quadrat is suitable for sampling or observing plants, slow-moving animals, and some aquatic organisms.
A photo-quadrat is a photographic record of the area framed by a quadrat. It may use a physical frame to indicate the area, or may rely on fixed camera distance and lens field of view to automatically cover the specified area of substrate. (1985). 9780521249157, Cambridge University Press. ISBN 9780521249157 Parallel laser pointers mounted on the camera can also be used as scale indicators. The photo is taken perpendicular to the surface, or as close as possible to perpendicular for uneven surfaces.
The ecologist John Ernst Weaver applied the use of quadrats to the teaching of ecology in 1918.
long-term studies, the same quadrats can be revisited after their initial sampling. Methods of precisely relocating the area of study vary widely in accuracy and include measurement from nearby permanent markers, use of total station Theodolite, consumer-grade GPS, and differential GPS.
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